Pipette



March 29, 1960 R. a. KELLETT PIPETTE Filed April 2a. 1958 NVENTOR.

RODERICK G- KELLET T PIPETTE Roderick G. Kellett, Villanova, Pa., assignor to Smith,

Kline 8: French Laboratories, Philadelphia, Pa., a corporation of Pennsylvania Application April 28,1958, Serial No. 731,321

1 Claim. (Cl. 73425.4)

This invention relates to a pipette and, more particularly, relates to a pipette which prevents liquid in the pipette from reaching the users mouth.

There are basically two general types of pipettes. One is open throughout its length and is by far the easier of the two to use. The disadvantage lies in the fact that the operator can draw the material being pipetted up into his mouth. Since the material is frequently an acid or other dangerous material, there is a distinct hazard which might be fatal. The other style is bulb operated and i safer but has the disadvantage of being much slower. There is also a hazard in inserting the pipette into the bottom of the bulb as the pipette may snap and cut the operator.

The primary object of this invention is to eliminate the hazard involved in using the conventional open tube pipette without the necessity of employing a bulb with its inconveniences and hazards.

This and other objects of this invention will become apparent on reading the description in conjunction with the drawings in which:

Figure l is an elevation, partially broken away, of a pipette in accordance with this invention;

Figure 2 is a section taken on the plane indicated by the line 2-2 in Figure 1;

Figure 3 is an enlarged view of the valve portion of the pipette of Figure 1, showing it full of liquid;

Figure 4 is an elevation, partially broken away, of a modified pipette in accordance with this invention;

Figure 5 is a section taken on the plane indicated by the line 5--5 in Figure 4;

Figure 6 is an elevation, partially broken away, of a modified pipette in accordance with this invention; and

Figure 7 is a horizontal section taken on the plane indicated by the line 77 in Figure 6.

As shown in Figures 1 through 3, a pipette 2 comprises a tube 4, preferably of glass, having a reduced intake end 6 and a suction end 8. Because of the safety features of this pipette, the opening at the reduced end 6 might be made larger than is normal, thereby speeding the operation of pipetting. A float valve 10 lies within the upper end of tube 4 and has a ball portion 12 and a stem r 14. Stop ring 16 acts to limit the downward travel of ball portion 12. Ring 18 forms a valve seat being engaged by ball portion 12.

An opening 20 in tube 4 is provided adjacent and below stop ring 16. Tube 4 is also provided with a line 22 indicating the desired level of liquid for carrying a predetermined amount of liquid in the pipette.

In operation, the user sucks on end 8 with the end 6 immersed in the desired liquid. A finger is used to close ofl opening 20. The suction raises valve 10 off States Patent stop ring 16, the suction being controlled so as to keep 2,930,238 Patented Mar. 29, 19 60 Assuming that pipette 2 contains liquid in an amount suflicient to seat valve 10 against seat 18 and it is now desired to release the contained liquid, the user removes his mouth and the liquid runs downwardly out of tube 4. The lowering of the liquid lowers valve 10 against stop ring 16. Since ring 16 and valve 10 may act to stop the flow of air down tube 4, the users finger is removed from opening 20 as the liquid drops below it to prevent the creationof a vacuum.

The stem 14 of valve 10 helps to keep the ball portion 12 centered in tube 4 but i not necessary.

A modified form of the invention is shown in Figures 4 and 5. A pipette 30 has a tube 32 (shown broken away). A cylindrical float valve 34 having ends 36 and 38 lies within tube 32. The downward travel of valve 34 is limited'by stop ring 40. A ring 42 forms a valve seat above valve 34.

Tube 32 has an opening 44 which opens into a chamber 46 formed by blister 48 which extend above the level of ring 42. An opening 50 in blister 48 connects chamber 46 to the atmosphere. Opening 50 is located above the level of ring 42.

The operation of this embodiment is substantially the same as that of the embodiment of Figure 1. If the level of liquid rises sufficiently, it will lift valve 34 to the seat formed by ring 42 and thus the flow of liquid to the users mouth will be safely blocked. Since opening 50 is above the level to which the liquid can rise the liquid will never come in contact with the users finger. As the liquid runs out, valve 34 lowers onto ring 40 but air is supplied to tube 32 via opening 50, chamber 46 and opening 44.

A further embodiment is shown in Figure 6. A pipette 60 has a tube 62 with a suction end 64 and a tube 66 with an intake end 68 connected by a bowl 70. A float valve 72 is located within bowl 7G. Bosses -74 prevents valve 72 from seating against the lower surface of boa/1 70. The upper reduced end 76 of bowl 70 acts as a seat for valve 72.

' In operation, if fluid is drawn up tube 66 and into bowl 70, valve 72 will be floated upwardly until it seats against reduced end 76 which blocks the flow of fluid from passing upwardly into the users mouth.

As the liquid is released the valve 72 is lowered onto bosses 74 which support it above the lower end of bowl 70 thus permitting air to pass downwardly between bowl 70 and valve 72.

It will be appreciated that this embodiment diifers from those previously described by eliminating the necessity for an air opening through the wall of the pipette tube by providing a stop for the valve which, being discontinuous, does not block the flow of air between the valve and the .stop. The previously described embodiments can readily be modified by making the stop rings discontinuous and eliminating theair openings in the tube walls.

The float Valves of the above described embodiments will have a specific gravity such that it will float in the liquid with which it is to be used and yet of sufiicient specific gravity to prevent it from being drawn into the valve seat 76 by the applied suction. The float valves may be constructed of any suitable materials such as synthetic resins, glass or metals, the specific gravity being readily adjusted by varying the valve from a solid member to a' thin shell. V

It is not desired to be limited except as set forth in the following claim.

What is claimed is:

A pipette comprising a tube having an intake end and v eeaoase i 3 4 a suction end, a fioat valve in said tube, a stop in said References Cited in the file of this patent tube to the travel Of said valve towards thfi intake P end of the tube, a seat for the valve between said stop and the suction end of the tube, an opening for the 531044 w 1896 2,688,867 Trainor Sept. 14, 1954 passage of air in said tube below said stop, and a blister 5 formin a chamber in communication with said opening, said blister having an opening thcrethrough above the FOREIGN PATENTS level of the valve seat. 116,797 Germany Jan. 21, 1901 

